Inhibited motor oils



Patented May 16, 1939 UNITED STATES PATENT orricr.

I INHIBITED MOTOR OILS ration of Delaware No Drawing. Application May 8,1936,

Serial No. 78,645

10 Claims.

This invention relates to superior mixed inhibitors which are especiallyadapted to reduce deterioration of lubricating oils in the presence ofair at high temperatures, such as those employed for lubricatinginternal combustion engines. More specifically, it deals with theproduction of lubricating oil inhibitors comprising a mixture of anorganic high temperature oxidation inhibitor and a metallo organiccompound of a metal of the class of bismuth, antimony and tin, as wellas compositions containing such mixtures.

Recent systematic research has disclosed that at least two classes ofinhibitors are effective in i5 retarding or suppressing thedeterioration of mineral lubricating oils in presence of air, moisture,metals, and the like. One type, exemplified by alpha naphthol, is activeat ordinary temperatures up to about 200-300 F. Above this temperatureit loses its activity and the oil be haves in the same manner as anuninhibited oil. Hence, although an inhibitor of this type may besatisfactory for turbine lubrication in which the temperature rarelyexceeds 250 F.,

it is valueless for lubricating automotive internal to a temperature of450-500 F. or higher in the proximity of the combustion zone.

The other type of inhibitors is the class of compounds which are veryeffective at elevated temperatures, especially in the neighborhood of400-500 F., although the members of this group may or may not have someactivity at lower temperatures. These materials are particularly 35useful in suppressing or retarding the deterioration of lubricating oilsfor internal combustion engines, and especially for aviation engineswhich operate at excessively high temperatures.

Of the numerous tests employed for judging the ability of an oil toresist deterioration at high temperature in an engine, the cone test hasbeen found to give data Which most closely approach results obtained inthe C. F. R. (Cooperative Fuel Research) test engine. In the cone test adetermined volume of a given oil is allowed to flow slowly over an openheated metal (generally steel) cone having a circumferential groovemilled out in screw fashion on the periphery so as to allow a time ofcontact of about one minute between the heated steel surface and theoil. A total volume of 60 00.01 oil is allowed to flow over this coneduring a period of 2 hours to obtain this rate. The temperature of thecone is generally kept at 250 C. (482 -F.), this tem- 55 perature havingbeen found to give most concombustion engines in which the oil issubjected cordant data with engine results. The cone is weighed beforethe test. After all of the oil is run over the metal surface, the coneis washed with naphtha. to remove adhering oil and the total deposit isobtained by the difference in weight. This value is generally reportedin grams, the higher value showing a poorer oil. The same oil may bepassed over the cone two. three or more times to give a betterindication as to its resistance after each exposure. This test will bereferred to further in the discussion.

The stabilizing process employed in this invention, therefore, involvesthe use of a mixture of two organic-compounds, namely: (1) A solublearomatic high temperature oxidation inhibitor and (2) soluble metalloorganic com'pound of bismuth, tin and/or antimony. The former ispreferably used in excess of the latter. These may be added to thelubricating oil in small proportions neighboring the values of .01 to0.1 or 0.2 or even 0.5 or 1% of the individual compounds.

The first mentioned materials, i. e., the high temperature inhibitorsconsist broadly of high boiling organic compounds soluble in mineraloils and having the structure:

RXnR' where R and R may be aliphatic, cyclic (e. g., aromatic,heterocyclic, naphthenic, etc), or mixed groups. Either R. or B. mayeven be or contain an inorganic group. X is a negative element of GroupVI of the periodic table, such as sulfur, oxygen, selenium andtellurium, and covers structural groups such as -s-, -'s's, -sss,-ss-s-s, -s-,

' s =s S and the like; n is an integer of one or more, usually 1, 2, 3or 4.

Examples of such compounds are diamyl trisulfide (C5H11SSS-C5H11), amylalpha xanthogenacetic ethyl ester or compounds of the type ofOOo-Cmscscm.

and similar materials preferably those boiling above 200 C. atatmospheric pressure.

In my copending application Ser. No. 704,131, filed on December 27,1933, I have disclosedcertain soluble aromatic inhibitors which are veryefiective in retarding or suppressing deteriora- 5 tion of minerallubricating oils at high temperatures. These compounds comprise anaromatic group containing an oxidation inhibiting group (OH,NH2 or SH)and another organic group (either alkyl, aryl or aryl-alkyl) attached tothe aromatic nucleus by at least one member of I the negative elementsof Group VI of the periodic table, as for example sulfur, oxygen,selenium or tellurium atom. An example of such a material is thefollowing:

80 Where R is a substituent, preferably one which will increasesolubility in lubricating oils (e. g., halogen, alkyl and similargroups), R is an alkyl, aryl or aralkyl group, while n is an integer ofone or more, usually 1, 2, 3, or 4. The sulfur or oxygen may be in thefollowing structural group:

and the like. Specific examples of such compounds are di-tertiary butylphenol thio ether, tertiary amyl phenol disulfide, 4 butoxy Z-aminonaphthalene, their polymers, and the like.

Such inhibitors, as shown by cone data, are very efiective in initiallyreducing the deterioration rate of mineral lubricating oils. However,this effect is lost to a certain degree over an extended period of'time, as shown by the fact that the cone residue is increased when theoxidized oil is again repeatedly passed over the cone.

According to the present invention, the increase in rate ofdeterioration of the oil thus inhibited can be reduced to a considerableextent by the addition thereto of the second mentioned material, i. e.,a soluble organo metallic compound of bismuth, tin, or antimony.Examples of such compounds are triphenyl bismuth, triphenyl tiniodide,trimethyl triphenyl distannane, tetra propyl tin, tetra isobutyl tin,triphenyl stibine, and the like. Apparently this class or organometallic compounds, though often not as eifective by itself in reducingthe cone deposit as the high temperature inhibitors, exerts somestabilizing effect upon the latter to produce a much more resistantblend.

The effect will be more clearly understood from an examination of thefollowing test results:

Example 1 An SAE 50 grade lubricating oil (oil A) of about 100 viscosityindex prepared by hydrogenation of a Colombian crude oil fraction wassubjected to the cone test with and without the following blendingagents: 0.4% tertiary butyl phenol sulfide (blend B), 0.2% triphenylbismuth (blend C), 0.4% tertiary butyl phenol sulfide and 0.2% triphenylbismuth (blend D), 0.2% triphenyl tin iodide (blend E), and 0.4%tertiary butyl phenol sulfide and 0.2% triphenyl tin iodide (blend F).

The oils were passed three times over the previously, and the residuewas weighed after each pass. The results are as follows:

First pass Second pass Third pass As shown by the above data, blends Dand F, containing the mixed inhibitors, give the best results after thethird pass when compared with the noninhibited oil or the blends havingonly one inhibitor.

' Example 2 cone according to the test procedure described di-tertiarybutyl phenol thio ether with 0.2%

triphenyl bismuth (blend K).

'I'he'data are as follows:

1st pass 2d pass 0d pass 4th pass As seen from the above data, the mixedinhibitor blend (blend K) is much more superior after the fourth pass toany of the blends containing the individual compounds.

The lubricating oils used for the purposes of this invention are mineraloils such as Pennsylvania, Coastal, Mid-Continent, Venezuelan,Colombian, etc., suitable for use in internal combustion engines, say aslow as 30-45 viscosity at 210 F. to viscosities neighboring those ofbright stocks, as to 150 seconds at 210 F. Such oils may be of SAEgrades 10, 20, 30, 40, 50 or higher. Synthetic hydrocarbon oils are notexcluded. These lubricating oils may be in the crude form or partiallyor highly refined by distillation, treatment with selective solvents,chemical reagents, hydrogenation, voltolization, absorptive agents,dewaxing processes, and the like.

Especially preferred are those mineral oils having high viscosityindices, 1. e., viscosity'indices in the neighborhood of 70, 80, or toand sometimes up to 120. Such oils tend to deteriorate more rapidly inhigh temperature internal combustion engines than other mineral oils,and hence are much more improved in value by this invention.Furthermore, a fiat viscosity temperature curve inherent in such oils isgenerally desirable for engine operation.

The above inhibited blends may be used in conjunction with otherlubricating oil blending agents, such as pour inhibitors, thickeners. V.I. improvers, dyes, sludge dispersing agents, extreme pressurelubricants, metallic soaps, colloidal solids, voltolized mineral orfatty oils or waxes, and the like.

Although there have been shown and described specific embodiments ofthis invention, many modifications thereof are possible. The invention,therefore, is not to be restricted except insofar as is necessitated bythe prior art and by the spirit of the appended claims.

I claim: 1. Composition of matter comprising a visco mineral lubricatingoil containing a small proportion of a soluble organic oxidationinhibitor 5 having a boiling point above 200 C. at atmospheric pressureand possessing the structure where R and R are organic groups, X is anegam tive element of Group VI of the-periodic system,

and n is an integer from 1 to 4, and a small proportion of a solublemetallo-organic compound of a metal of the class consisting of bismuth,antimony and tin, said metallo-organic compound containing acarbon-metal linkage.

2. Composition of matter according to claim 1 in which the viscousmineral oil has a viscosity index above 70.

3. Composition of matter according to claim 1 2 inhibitor is'greaterthan the proportion of metallo organic compound.

4. Composition of matter according to claim 1 in which the proportion oforganic oxidation in- 25 hibitor is from 0.01% to 1%.

5. Composition of matter according to claim 1 in which the proportion ofmetallo organic compound is irom 0.01% to 1%,

6. Composition of matter comprising a mineral lubricating oil containing0.4% of an alkylated in which the proportion of organic oxidation phenolthin-ether, and 0.2% of triphenyl bismuth.

7. Composition of matter according to claim 1 in 'which the oxidationinhibitor possesses the structure Rr-Xn-R' where R is an aromatic grouphaving an oxida-, tion inhibiting group, Rf is an organic group, X is anelement selected from the group consisting of oxygen and sulphur, and nis an integer from 1 to 4.

8- Composition of matter according to claim 1 in which the proportion oforganic oxidation inhibitor is from 0.01% to 1%, and in which theproportion of metallo-organic compound is from 0.01% to 1%.

9. Composition of matter comprising a mineral lubricating oil containing0.4% of an alkylated phenol thio-ether, and 0.2% of a metallo organiccompound .of a metal of the class con-. sisting of bismuth, antimony andtin, said metallo-organic compound containing a carbonmetal linkage.

10. Composition of matter comprising a mineral lubricating oilcontaining 0.4% of an alkylated phenol thio-ether, and 0.2% of triphenyltin iodide.

RAPHAEL ROSEN.

